bug#23164: 25.1.50; xref-find-definitions with local tags-file-name fails

bug#23164: 25.1.50; xref-find-definitions with local tags-file-name fails

[Johan Claesson]

Hi,

emacs -Q 

(fundamental-mode)
(setq-local tags-file-name "/dev/zero")
(xref-find-definitions "foo")

Fails with (wrong-type-argument stringp nil) in
visit-tags-table-buffer.

The problem also occurs when tags-file-name points to a valid TAGS
file (the invalid /dev/zero was chosen just to make the recipe
short).

If tags-file-name have a global value there is no problem. 

It is the following line in visit-tags-table-buffer that fails. 

  (setq tags-file-name (tags-expand-table-name tags-file-name))

If this is protected with (when tags-file-name ...) then the problem
do not occur.  The same if the line is moved down and inside the
unless sexp that follows immediately.  If either is the right thing to
do i don't know.  But it seem a bit strange to assume that
tags-file-name shall be non-nil at that point.  The problem occurs
when etags--xref-find-definitions calls visit-tags-table-buffer for
the second time.

Regards,

/Johan



In GNU Emacs 25.1.50.1 (x86_64-unknown-linux-gnu, X toolkit)
 of 2016-03-28 built on goblin
Repository revision: a30e7e12ed8465e2565dd318d921bc87f52ce18e
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Wrote /home/jcl/.newsrc.eld
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bug#23164: 25.1.50; xref-find-definitions with local tags-file-name fails

[Dmitry Gutov]

Hi there!

On 03/30/2016 11:52 PM, Johan Claesson wrote:

> emacs -Q
>
> (fundamental-mode)
> (setq-local tags-file-name "/dev/zero")
> (xref-find-definitions "foo")
>
> Fails with (wrong-type-argument stringp nil) in
> visit-tags-table-buffer.

I do see the error with tags-file-name set to /dev/zero.

> The problem also occurs when tags-file-name points to a valid TAGS
> file (the invalid /dev/zero was chosen just to make the recipe
> short).

Thanks for the report, but that doesn't seem to be the case here. At 
least if I replace "/dev/zero" with "~/vc/emacs/src/TAGS", the scenario 
doesn't lead to an error (I just get "not found"), and if I also use 
e.g. "CALLN" instead of "foo", the jump to the destination occurs as 
expected.

To be 100% sure we're trying the same code, could you build Emacs from 
the branch emacs-25? Is there anything else you can tell us to help 
reproduce the problem?

> If tags-file-name have a global value there is no problem.
>
> It is the following line in visit-tags-table-buffer that fails.
>
>   (setq tags-file-name (tags-expand-table-name tags-file-name))
>
> If this is protected with (when tags-file-name ...) then the problem
> do not occur.  The same if the line is moved down and inside the
> unless sexp that follows immediately.  If either is the right thing to
> do i don't know.  But it seem a bit strange to assume that
> tags-file-name shall be non-nil at that point.

The preceding form tries to make sure to set it to the current value. 
Depending on the value of CONT, it will ask the user, use the current 
value, or delegate to some guessing logic. It's not 100% solid, though.

> The problem occurs
> when etags--xref-find-definitions calls visit-tags-table-buffer for
> the second time.

The assumption here is that the second time visit-tags-table-buffer is 
called from the tags file buffer. And that the previous invocation 
either set tags-file-name locally in that buffer, or at least set 
tags-table-list.

bug#23164: 25.1.50; xref-find-definitions with local tags-file-name fails

[Óscar Fuentes]

Dmitry Gutov <dgutov@yandex.ru> writes:

> Thanks for the report, but that doesn't seem to be the case here. At
> least if I replace "/dev/zero" with "~/vc/emacs/src/TAGS", the
> scenario doesn't lead to an error (I just get "not found"), and if I
> also use e.g. "CALLN" instead of "foo", the jump to the destination
> occurs as expected.

I can reproduce it here with an existing TAGS file, on emacs -Q.

GNU Emacs 25.0.92.3 (x86_64-unknown-linux-gnu, X toolkit) of 2016-04-03

at commit fc3cd53900eb5e80b91b6d2615b3800fd2f59c16

Debugger entered--Lisp error: (wrong-type-argument stringp nil)
  expand-file-name(nil)
  tags-expand-table-name(nil)
  visit-tags-table-buffer(t)
  etags--xref-find-definitions("foo")
  #[514 "\300!\207" [etags--xref-find-definitions] 4 "\n\n(fn BACKEND SYMBOL)"](etags "foo")
  apply(#[514 "\300!\207" [etags--xref-find-definitions] 4 "\n\n(fn BACKEND SYMBOL)"] etags "foo")
  xref-backend-definitions(etags "foo")
  xref--find-xrefs("foo" definitions "foo" nil)
  xref--find-definitions("foo" nil)
  xref-find-definitions("foo")
  eval((xref-find-definitions "foo") nil)
  elisp--eval-last-sexp(nil)
  eval-last-sexp(nil)
  funcall-interactively(eval-last-sexp nil)
  call-interactively(eval-last-sexp nil nil)
  command-execute(eval-last-sexp)

bug#23164: 25.1.50; xref-find-definitions with local tags-file-name fails

[Johan Claesson]

I can also reproduce it on emacs-25 (commit f501116).
With valid TAGS file or /dev/zero.
I get the same backtrace.

Regards,

/Johan

Óscar Fuentes <ofv@wanadoo.es> writes:

> Dmitry Gutov <dgutov@yandex.ru> writes:
>
>> Thanks for the report, but that doesn't seem to be the case here. At
>> least if I replace "/dev/zero" with "~/vc/emacs/src/TAGS", the
>> scenario doesn't lead to an error (I just get "not found"), and if I
>> also use e.g. "CALLN" instead of "foo", the jump to the destination
>> occurs as expected.
>
> I can reproduce it here with an existing TAGS file, on emacs -Q.
>
> GNU Emacs 25.0.92.3 (x86_64-unknown-linux-gnu, X toolkit) of 2016-04-03
>
> at commit fc3cd53900eb5e80b91b6d2615b3800fd2f59c16
>
> Debugger entered--Lisp error: (wrong-type-argument stringp nil)
>   expand-file-name(nil)
>   tags-expand-table-name(nil)
>   visit-tags-table-buffer(t)
>   etags--xref-find-definitions("foo")
>   #[514 "\300!\207" [etags--xref-find-definitions] 4 "\n\n(fn BACKEND SYMBOL)"](etags "foo")
>   apply(#[514 "\300!\207" [etags--xref-find-definitions] 4 "\n\n(fn BACKEND SYMBOL)"] etags "foo")
>   xref-backend-definitions(etags "foo")
>   xref--find-xrefs("foo" definitions "foo" nil)
>   xref--find-definitions("foo" nil)
>   xref-find-definitions("foo")
>   eval((xref-find-definitions "foo") nil)
>   elisp--eval-last-sexp(nil)
>   eval-last-sexp(nil)
>   funcall-interactively(eval-last-sexp nil)
>   call-interactively(eval-last-sexp nil nil)
>   command-execute(eval-last-sexp)

bug#23164: 25.1.50; xref-find-definitions with local tags-file-name fails

[Johan Claesson]

Hi again,

I tried again this time with the TAGS of Emacs itself (emacs/src/TAGS).
And like you have already established the problem does not occur in this
scenario.  It does occur with other valid TAGS files, though.  

After a little bit of tracing i think the difference that matters is
that emacs/src/TAGS includes two other TAGS file in the very last lines:

\f
../lisp/TAGS,include
\f
../lwlib/TAGS,include

I was not aware of this feature with TAGS files including other TAGS
files before but after invoking xref-find-definitions emacs is visiting
all 3 TAGS files (src/TAGS, lisp/TAGS and lwlib/TAGS).  And
xref-find-definitions loops through them all.

If these last lines in emacs/src/TAGS are deleted the problem occurs.

It also occur with other simple TAGS files that do not include other
TAGS files.  And the TAGS file i was using when observing the problem
the first time was this kind of simple TAGS file.

Same in master and emacs-25.

Regards,

/Johan




Óscar Fuentes <ofv@wanadoo.es> writes:

> Dmitry Gutov <dgutov@yandex.ru> writes:
>
>> Thanks for the report, but that doesn't seem to be the case here. At
>> least if I replace "/dev/zero" with "~/vc/emacs/src/TAGS", the
>> scenario doesn't lead to an error (I just get "not found"), and if I
>> also use e.g. "CALLN" instead of "foo", the jump to the destination
>> occurs as expected.
>
> I can reproduce it here with an existing TAGS file, on emacs -Q.
>
> GNU Emacs 25.0.92.3 (x86_64-unknown-linux-gnu, X toolkit) of 2016-04-03
>
> at commit fc3cd53900eb5e80b91b6d2615b3800fd2f59c16
>
> Debugger entered--Lisp error: (wrong-type-argument stringp nil)
>   expand-file-name(nil)
>   tags-expand-table-name(nil)
>   visit-tags-table-buffer(t)
>   etags--xref-find-definitions("foo")
>   #[514 "\300!\207" [etags--xref-find-definitions] 4 "\n\n(fn BACKEND SYMBOL)"](etags "foo")
>   apply(#[514 "\300!\207" [etags--xref-find-definitions] 4 "\n\n(fn BACKEND SYMBOL)"] etags "foo")
>   xref-backend-definitions(etags "foo")
>   xref--find-xrefs("foo" definitions "foo" nil)
>   xref--find-definitions("foo" nil)
>   xref-find-definitions("foo")
>   eval((xref-find-definitions "foo") nil)
>   elisp--eval-last-sexp(nil)
>   eval-last-sexp(nil)
>   funcall-interactively(eval-last-sexp nil)
>   call-interactively(eval-last-sexp nil nil)
>   command-execute(eval-last-sexp)

bug#23164: 25.1.50; xref-find-definitions with local tags-file-name fails

[Johan Claesson]

Ooops, i see that the formatting of my last email got messed up because 
it includes some form-feeds (^L).  Here is the same message again
without evil form-feeds :)

Hi again,

I tried again this time with the TAGS of Emacs itself (emacs/src/TAGS).
And like you have already established the problem does not occur in this
scenario.  It does occur with other valid TAGS files, though.  

After a little bit of tracing i think the difference that matters is
that emacs/src/TAGS includes two other TAGS file in the very last lines:

^L
../lisp/TAGS,include
^L
../lwlib/TAGS,include

I was not aware of this feature with TAGS files including other TAGS
files before but after invoking xref-find-definitions emacs is visiting
all 3 TAGS files (src/TAGS, lisp/TAGS and lwlib/TAGS).  And
xref-find-definitions loops through them all.

If these last lines in emacs/src/TAGS are deleted the problem occurs.

It also occur with other simple TAGS files that do not include other
TAGS files.  And the TAGS file i was using when observing the problem
the first time was this kind of simple TAGS file.

Same in master and emacs-25.

Regards,

/Johan



> Óscar Fuentes <ofv@wanadoo.es> writes:
>
>> Dmitry Gutov <dgutov@yandex.ru> writes:
>>
>>> Thanks for the report, but that doesn't seem to be the case here. At
>>> least if I replace "/dev/zero" with "~/vc/emacs/src/TAGS", the
>>> scenario doesn't lead to an error (I just get "not found"), and if I
>>> also use e.g. "CALLN" instead of "foo", the jump to the destination
>>> occurs as expected.
>>
>> I can reproduce it here with an existing TAGS file, on emacs -Q.
>>
>> GNU Emacs 25.0.92.3 (x86_64-unknown-linux-gnu, X toolkit) of 2016-04-03
>>
>> at commit fc3cd53900eb5e80b91b6d2615b3800fd2f59c16
>>
>> Debugger entered--Lisp error: (wrong-type-argument stringp nil)
>>   expand-file-name(nil)
>>   tags-expand-table-name(nil)
>>   visit-tags-table-buffer(t)
>>   etags--xref-find-definitions("foo")
>>   #[514 "\300!\207" [etags--xref-find-definitions] 4 "\n\n(fn BACKEND SYMBOL)"](etags "foo")
>>   apply(#[514 "\300!\207" [etags--xref-find-definitions] 4 "\n\n(fn BACKEND SYMBOL)"] etags "foo")
>>   xref-backend-definitions(etags "foo")
>>   xref--find-xrefs("foo" definitions "foo" nil)
>>   xref--find-definitions("foo" nil)
>>   xref-find-definitions("foo")
>>   eval((xref-find-definitions "foo") nil)
>>   elisp--eval-last-sexp(nil)
>>   eval-last-sexp(nil)
>>   funcall-interactively(eval-last-sexp nil)
>>   call-interactively(eval-last-sexp nil nil)
>>   command-execute(eval-last-sexp)

bug#23164: 25.1.50; xref-find-definitions with local tags-file-name fails

[Dmitry Gutov]

On 04/05/2016 12:24 AM, Johan Claesson wrote:

> It also occur with other simple TAGS files that do not include other
> TAGS files.  And the TAGS file i was using when observing the problem
> the first time was this kind of simple TAGS file.

Right, thank you.

Apparently, the long-standing way to make it work is to call 
visit-tags-table with non-nil second argument, instead of just using 
setq-local. So, this seems to work correctly:

(fundamental-mode)
(visit-tags-table "~/examples/ruby/TAGS" t)
(xref-find-definitions "a")

It performs more work in advance, though, and I'm not sure what's the 
big picture with keeping variables like tags-table-list global anyway.

Here's a patch you can try that makes etags--xref-find-definitions work 
with your original scenario, but I'm not 100% sure it's good code. The 
proper solution to setting tags-file-name locally probably looks different.

diff --git a/lisp/progmodes/etags.el b/lisp/progmodes/etags.el
index a2a0df2..856d26b 100644
--- a/lisp/progmodes/etags.el
+++ b/lisp/progmodes/etags.el
@@ -2111,6 +2111,7 @@ etags--xref-find-definitions
                                 tags-case-fold-search
                               case-fold-search)))
      (save-excursion
+      (visit-tags-table-buffer) ; Workaround for bug#23164
        (while (visit-tags-table-buffer (not first-time))
          (setq first-time nil)
          (dolist (order-fun (cond (regexp? find-tag-regexp-tag-order)

bug#23164: 25.1.50; xref-find-definitions with local tags-file-name fails

[Johan Claesson]

Dmitry Gutov <dgutov@yandex.ru> writes:
>
> (fundamental-mode)
> (visit-tags-table "~/examples/ruby/TAGS" t)
> (xref-find-definitions "a")

This does not work for me.  I run into the same error.  

> Here's a patch you can try that makes etags--xref-find-definitions
> work with your original scenario, but I'm not 100% sure it's good
> code. The proper solution to setting tags-file-name locally probably
> looks different.

Thanks, this patch works perfectly as far as i can see. 

Regards,

/Johan

bug#23164: 25.1.50; xref-find-definitions with local tags-file-name fails

[Josiah Schwab]

Hello,

I receive an error from commands like the original bug

> (setq-local tags-file-name "fruits/TAGS")
> (xref-find-definitions "apple")

and the proposed workaround

> (visit-tags-table "fruits/TAGS" t)
> (xref-find-definitions "apple")

under emacs 25.1 and git master (at c542fab).

I used a trivial TAGS file, available from

  https://github.com/jschwab/emacs-tags-issues/blob/master/fruits/TAGS

but any simple tags file (that doesn't include other TAGS files; see
earlier in this thread) ought to work.

Josiah